Science 1206

1

Chapter 13,14,15

Weather dynamics is the study of how the motion of water and air causes weather patterns.

Energy from the Sun drives the motion of clouds, air, and water.

Major components of Earth that influence weather are:

1. air: atmosphere2. land forms: lithosphere3. water ( all states): hydrosphere

About 70% of Earth’s surface is covered by oceans.

2

The atmosphere contains air, water vapour, and particles of dust and chemicals, all of which affect weather, especially when the atmosphere is in motion.

3

Weather is the set of environmental conditions encountered from day to day.

Climate is the set of environmental conditions averaged over many years.

4

https://www.youtube.com/watch?v=YbAWny

7FV3w

Weather vs Climate

Longitude is the angle measured East or West from the 0 degree line which passes through Greenwich, England.

Latitude is the angle measured North or South of the equator.

5

6

The Tropic of Cancer is at 23.5 degrees [N] latitude. It is the most northerly location reached by the Sun’s vertical rays on the first day of summer, June 21, each year.

The Arctic Circle is at 66.5 degrees [N] latitude. It is the most northerly location reached by any of the Sun’s rays on the first day of winter, December 21.

In the southern hemisphere we have the Tropic of Capricorn 23.5 degrees [S] latitude and the Antarctic Circle 66.5 degrees [S] latitude .

The region between the Tropic of Cancer and the Tropic of Capricorn is referred to as the tropics.

Most of Canada’s population lives in the mid-latitude region.

7

Read Chapter 13

8

9

Most of the energy used on Earth to sustain life and cause changing weather systems comes from the Sun.

The average surface temperature is 15 degrees C.

Different types of EM energy are emitted from the Sun.

Energy can be transferred from one place to another by 4 methods:

1) Radiation2) Conduction3) Convection4) Advection

10

The transfer of energy by means of waves or particles. Radiation does not need a medium.

The waves can travel from the Sun, through space, and reach Earth.

1. Visible light is energy that can travel through space. 2. Radio waves3. Microwaves4. X-rays5. Gamma rays6. Infrared rays

https://www.youtube.com/watch?v=5GoZZKcNZiQRadiation Heat Transfer

1. Radiation

11

The set of waves that can travel through empty space at the speed of light is called the

electromagnetic spectrum.

12

The other methods of energy transfer require particles of matter.

Conduction -the transfer of energy through the collision of particles. Occurs most easily in metals , but also to a smaller extent in rock, sand soil and water.

2. Conduction

https://www.youtube.com/watch?v=9joLYfayee8

Conduction

13

Convection and advection are the transfer of energy by the movement of particles in a fluid.

A fluid is either a liquid (water) or a gas(atmosphere).

Convection transfers energy vertically . Advection transfers energy horizontally.

Weather systems involve convection and advection.

3. Convection and 4. Advection

https://www.youtube.com/watch?v=O3N9XyTkSBI (Heat Transfer Review)

https://www.youtube.com/watch?v=VxGIiOTuAIs

Convection

https://www.youtube.com/watch?v=BE0BBHyX0l8

Advection Fog

14

The portion of energy reflected depends on the albedo of the material.

Clean snow has a high albedo, it reflects a lot of incoming energy. Black soil has a low albedo, it absorbs more energy than it reflects.

Any object or material that absorbs energy and becomes warmer is called a heat sink. Water has a higher albedo than land and soil, the oceans are good heat sinks.

When solar energy hits water , the water begins to move(convection), and transfer energy deep into the oceans.

Soil and rock are poor heat sinks. Heat is conducted slowly into these materials.

Review: Albedo and heat sinks

15

The measure of how much heat a substance requires to increase its temperature or how much heat it releases as its temperature decreases.

◦ Water has a high heat capacity. This means it can hold a lot of heat.

Heat Capacity

Clouds have a duel role:

1) Quite simply clouds act as a blanket.◦ Cloudy nights: traps heat keeping the air warm.

◦ Clear night sky: heat escapes and air cools quickly.

2) Keep the earth cool during the day.◦ The formation of white cloud cover reflects the

sun's energy away.

16

17

Energy Transfer Worksheet

19

All of Earth’s water, both fresh and salt, forms what is called the hydrosphere.

About 70% of Earth’s surface is covered by water.

Freshwater makes up 2.5% of the total water on Earth. Most of this occurs as polar ice.

Hydrosphere

https://www.youtube.com/watch?v=ZyWCb

YnC7cI

Hydroshpere

20

and transpiration

21

6 forms of Precipitation

1 2 3 4

6 - Fog

5

See P. 556 in text

Water vapor is responsible for:

1. clouds

2. fog

3. rain

4. snow

22

23

Water Cycle

Return to step 1

24

25

Worksheet # 5 – Precipitation Worksheet

Water cycle does not only transport water BUT it also transports and

transfers energy by the process of convection and conduction as well

as changes of state – evaporation and condensation.

A large amount of energy is needed to overcome the forces of

attraction between water molecules in the atmosphere in order for

water to evaporate, while a large amount of energy is released

when water molecules condense!

The thin layer of gases that surround the earth is the atmosphere. (about 10 km thick)

The atmosphere is where all the weather happens.

The atmosphere acts like a blanket which controls the temperature of the earth.

27

The earth's atmosphere is made up of dust and a mixture of invisible gases. Some of these gases include:

Nitrogen (N2) 78%

Oxygen (O2) 21%

Other gases: 1% combined

[water vapor, argon, carbon dioxide, neon, helium, krypton, hydrogen, ozone...]

28

Nitrogen and ozone act as a protection shield that blocks out harmful radiation from space( UV ).

Oxygen is essential for life. Plants produce oxygen and we breathe it in.

Carbon dioxide is essential for life too. We breathe out carbon dioxide and plants breathe it in.

29

The atmosphere can be divided up into distinctive layers.

Exosphere

Thermosphere

Mesosphere

Stratosphere

Tropopause

Troposphere

30

The atmosphere is made up of areas of different densities and temperature.

31

32

33

34

35

36

37

38

39

Worksheet # 8 - Layers of the Atmosphere

Layer and Gas in the Atmosphere Assignment – Worksheet # 9

https://www.youtube.com/watch?v=AkaY1dvZer4 - Rap

https://www.youtube.com/watch?v=dQPyNY2WIdw - Song

40

41

1)Anemometer – is a device used to

measure wind speed

42

43

44

45

46

The word aneroid means without liquid.

47

48

High air pressure in a region indicates fair weather while low pressure indicates that storms are more likely.

Low pressure –

joints and arthritis

acts up!!

49

50

51

Weather satellite

Weather Balloons

Computers

52

53

Water in the Air

Humidity

Humidity:◦ a measure of the amount

of water vapor in the air

◦ Warm air can hold more moisture then cold air

Relative Humidity:◦ The measure of the

amount of water vapor compared to the Maximumamount possible

Saturated Air◦ Relative humidity is 100%

◦ Over 100% results in condensation

Dew Point◦ Temp at which dew forms

◦ As air gets colder, it holds less moisture

◦ Releases excess as dew

Large amounts of energy is needed to

overcome the forces of attraction

between water molecules in the

atmosphere in order for water to

evaporate, while large amounts of

energy is released when water

molecules condense!!

Figure 1, pg. 558 – Maximum Amounts

%100ionconcentrat maximum

ionconcentratHumidity Relative x

Ex 1:

What is the relative humidity if 1.9 g/kg of water in air is present at 0oC?

Ex 2:

What is the conc of H2O in the air at 20oC if the relative humidity is 50%?

%100ionconcentrat maximum

ionconcentratHumidity Relative x

Ex 1:

What is the relative humidity if 1.9 g/kg of water in air is present at 0oC?

Ex 2:

What is the conc of H2O in the air at 20oC if the relative humidity is 50%?

Dry Bulb Wet Bulb Relative Humidity

22 17

18 14

32 30

32 22

Higher humidity◦ causes perspiration to evaporate slowly.

◦ Sweating doesn’t cool us as well

Low humidity◦ Air is dryer

◦ Skin may be

uncomfortable

Humidex:◦ Reports how hot the

◦ humidity makes us feel

• A cloud that forms near the ground

• Can form on cool, cloudless nights

• When warm air passes over snow-covered ground

• When moist sea air drifts over a cold current

• When moist air rises up a mountain side

Forms when warm moist air moves over a colder surface (land or water) releasing its moisture as very fine water droplets.

61

See Fig 2, pg. 556

Hail:

◦ created in cumulonimbus clouds

◦ Frozen raindrops are circulated up and down

◦ Layers of ice are formed

Dew:◦ Water vapour condenses near

the ground as the air cools

◦ Cold Days : Frost

63

Water in the air assignment

Worksheet 4

Weather can be affected by:◦ A) Sun

◦ B) Water

◦ C) Landforms

◦ D) Atmosphere

64

Weather can be affected by local landforms in a specific area

Thermal:

◦ A local convection current set up during the day

◦ The sun heats the ground, causing the air to rise

◦ From water to land

◦ A thermal formed near water

◦ The sun heats the land. The air rise, and a cool breeze blows in from the water.

Where are the

highs and

lows?

from land to water◦ After sunset, the land cools quickly.

◦ Air above the warmer water rises, replaced by air from the land.

Where are the

highs and

lows?

When air moves over water it picks up moisture. In winter, water is warmer then the land (more moisture)

When the air reaches the cold land, the moisture becomes snow

A gentle warm, dry wind on the leeward side of the Rocky mountains

70

Atmospheric pressure is the pressure the air exerts as gravity pulls it toward the center of Earth.It is greatest at sea level, where the molecules are closet together.

At higher altitudes atmospheric pressure decreases.

Pressure gradient is a measure of the amount the atmospheric pressure changes across a set distance.Pressure gradients can be vertical or horizontal.

71

The atmosphere is made up of areas of different densities and temperature.

72

1. Altitude – (elevation)

2. Temperature – Particle theory

3. Density-

73

74

75

76

77

78

79

Gravity pulls down on all matter.

Gases are matter and gravity pulls down on them.

This is why the troposphere (layer closest to the earth) has 99% of all the gases in the atmosphere.

80

81

Worksheet: Air Pressure

Section 13.6

82

Sailors discovered that in certain areas the winds tend to blow in the same directions most of the time.

Close to the equator the winds would blow to the west (from the east).

Further North they found that the winds would blow most often to the east (from the west).

This regular pattern of winds is known as prevailing winds.

83

Wind is a movement of air in the atmosphere from areas of high pressure to areas of low pressure.

84

85

Winds that affect large areas in regular patterns.

Blowing to the east they called the Northeast trade winds.

The winds blowing from the west (taking them back home) were called the mid-latitude Westerlies (prevailing Westerlies).

86

87

Spin

The earth rotates east to west.

As the earth spins it deflects the wind.

◦ Winds blowing north get deflected to the right.

◦ Winds blowing south get deflected to the left.

The deflection of the wind caused by the earth's rotation is called the Coriolis effect.

88

89

Earth’s rotation causes anything that moves, to appear to change direction. This apparent change of direction of a moving object in a rotating system is called the

Coriolis effect.

Viewed above the North pole, Earth rotates eastward or counter clockwise.

Objects in the Northern hemisphere appear to move to the right.

In the Southern hemisphere moving objects appear to move to the left.

90

91

92

93

Early explorers like Columbus used trade winds to cross the Atlantic Ocean.

94

Prevailing winds are caused by convection currents and rotation.

In the Northern hemisphere....

• Solar energy strikes the equator, heating the air, land, water• The warm air rises and expands, leaving a low pressure area• Rising air moves northward• At 30 degrees latitude the cooled air sinks, creating high pressure

• The moving air is twisted right as it moves south (Northeast Trade Winds)

95

In the Northern hemisphere.....

At 30 degrees latitude descending air is deflected northward, to an area of low pressure at 60 degrees latitude.

The surface air moving northward to the low pressure area twists to the right causing the mid-latitude westerlies.

96

At the North Pole the air is cold and dense, so it sinks, creating a high pressure region. This surface air moves south, twisting to the right

and creating the polar easterlies.

A narrow band of spinning air is created in the places where these convection currents rise and fall.

The spinning causes the air to speed up creating a tube of fast moving air known as a jet stream.

The winds of the jet stream travel from west to east and can reach speeds of up to roughly 500 km/h.

97

Aircraft use this to their advantage when flying form west to east.◦ pick up to a 500 km/h tail wind which saves

time and fuel.

Going from east to west pilots try to avoid the jet streams.

Jet streams steer major

weather systems.

98

99

100

Jet Streams – high speed winds in the troposphere

(241 to 482 kilometres per hour)

101

102

Prevailing winds help to distribute large amounts of solar energy from the equator to colder parts of the world.

Convection currents create a return flow of air southward.

Prevailing winds carry moisture causing rain, snow.

Rising air is warm and moist.Falling air is cool and dry.

At 30 degrees N latitude we have cool, dry air. Many deserts are found in this latitude.

At 60 degrees N latitude two air systems meet and rise giving birth to winter storms.

103

Wind Assignment – Worksheet 6

- Worksheet 12

Section 13.9

104

In 1992 a container ship in the middle of the Pacific Ocean lost 29 000 bath tub toys over the side. Rubber duckies started washing ashore all over the west coast of North America.

In 1990 in a similar type accident 80,000 pairs of Nike shoes were swept off a Korean ship headed for the United states. Nike shoes started showing up from Hawaii to Oregon and as far north as Alaska.

These two accidents provided valuable information to oceanographers regarding ocean currents.

105

106

107

Another spill occurred in 1999.

An oceanographer is a scientist that studies ocean currents.

Ocean currents are compared to large conveyor belts that move around the globe.

The ocean currents circulate the sun’s energy from the equator to the poles.

108

109

They serve to warm the poles and at the same time cool the waters of the equator.

In other words the ocean current spread out the heat energy all over the earth so that one area doesn't become too hot or too cold.

110

The main cause of ocean currents is unequal heating of the ocean by the sun.

At the equator the sun strongly heats the water.

As the water warms is gets lighter (less dense) and begins to rise.

Cooler, denser water sinks and rushes in to replace the warmer water.

111

This movement of water creates enormous convection currents.

We see warm surface currents flowing toward the poles (N & S).

At the same time, we get cold deep water currents flowing toward the equator.

The surface currents are pushed along and steered around the earth by the prevailing winds.

112

113

The warmer the air is above a body of

water, the more water it is capable of holding.◦ Evaporation rate is high and clouds form.

◦ Large amounts of precipitation.

Colder water has cool and dry air above it.◦ Weather it brings is cool and dry.

114

115

Normal Year El Niño Year

116

During an El Niño year the Pacific Ocean undergoes a greater than normal amount of heating.

This disrupts and changes the normal patterns of convection currents and wind patterns in the Pacific Ocean.

117

During El Niño years:

the jet stream tends to push further north.

As result North America tends to receive warmer than normal average temperatures.

118

119

About every four to five years, a pool of cooler-than-normal water develops off South America.

This usually shifts the jet stream farther south which steers’ colder drier winters to the Canadian west.

120

(Chp 14, pg. 542)

121

Meteorology: The study of the atmosphere and weather forecasting

Weather System: ◦ A set of weather variables that move as a unit for a

few days

Air Mass:◦ Large body of air in which temp and moisture is

fairly uniform

6 different air masses – see chart next slide

Combinations of

◦ Maritime or Continental

(Moist or Dry)

◦ Tropical or Polar

◦ (Warm or cold)

Air Masses TemperatureMoisture

Content

Maritime Polar

(West Coast)

Maritime Polar

(East Coast)

Continental Polar

Maritime Tropical

(West Coast)

Maritime Tropical

(East Coast)

Continental Tropical

Front: the boundary between a cold air mass and a warm air mass

Warm front: the leading edge of a warm air mass

Cold front: the leading edge of a cold air mass

Occluded Front◦ cold front catches

up with a warm front; the warm air is lifted above the earth’s surface and is cut off (occluded) from the cooler air below

Stationary front: warm and cold air masses remains still for some time

A: Warm and Cold front meet

B:Main Stage:

Warm air is pushed up, lots of precipitation

C: Occluding Stage: Storm weakens as fronts combine

D:Final Stage

Flow of air dissipates, storm ends

Spins CCW in Northern Hemisphere

CW in Southern Hemisphere

Usually brings clear skies

Air moves outward from the centre of the high

Rotates clockwise in the Northern Hemisphere (CCW in S. Hemisphere)

134

Major Ocean Currents Assignment – Worksheet # 13

135